| Owing to their excellent mechanical properties,magnesium and its alloys have been widely used in automobile and electronics.Also,magnesium and its alloys are potential biomedical material,due to their outstanding biocompatibilities and biodegradation,and the mechanical properties are similar to the human bones,which can avoid “stress shielding” and the risk of reoperation.However,magnesium and its alloys cannot maintain sufficient mechanical integrity before the tissue or bone healed thanks to their rapid degradation.Therefore,it has been the focus of researches to reduce degradation and improve the biocompatibility.In the experiment,AZ60 magnesium alloys were used as the matrix,KH550 was used as silane coupling agent to prepare coating on the surface of matrix and then induce DCDP or calcium carbonate coatings on silane coating.The first step is that KH550 hydrolyzed and then coated on the surface of AZ60 magnesium alloys.The amount of KH550,the ratio between ethanol and water,the p H value of solution,hydrolysis time and the layers are the variables of the experiments and get the best parameters.The composition of coating were analyzed by FTIR,the morphologies were observed by SEM and the properties of corrosion resistance were detected by electrochemical workstation and immersion tests.The second step is that using silane coating induce DCDP or calcium carbonate coating on the surface of AZ60 magnsium alloys.The composition of composite coatings were characterized by FTIR and XRD,the morphologies were verified by SEM and the properties of anti-corrosion were tested by electrochemical workstation and immersion tests.The experiment results show that silane treatment by KH550 can effectively improve the corrosion resistance of magnesium when the amount of KH550 is 6%,the ratio in volume between alcohol and water is 1:9,the hydrolysis time is 6h,the p H value of solution is 11 and the layers of silane coating are 2.In this case,the morphologies of coating were flat and smooth,the corrosion potential increased by 0.337 V and the corrosion current density decreased to 1/14 of the pristine AZ60 magnesium alloy.Through the immersion tests,the silane coating can reduce the hydrogen rate and maintain the p H value of solution stable,reduce corrosion rate and has certain biocompatibility and bio-mineralization ability.The corrosion resistance of the matrix can be improved by the calcium carbonate coating coating induced by the silane coupling agent,and the DCDP coating can further improve the corrosion resistance of the samples.Calcium carbonate coating surface morphology is uniform and dense block,the corrosion potential is-1.3584 V and the corrosion current density is 13.202?A,the coating after immersion tests for 7 days appeared a certain degree of shedding and cracking;and DCDP coating is a fibrous shape on surface,conducive to the adhesion of cells on the surface,with good electrochemical properties,the corrosion potential is-1.0673 V and the corrosion current density is 0.4729?A,thus the corrosion resistance improved significantly.At the same time,the coating on the coating will form flocculent corrosion products,the main elements of corrosion product were Ca,P analyzed by EDS equipped with SEM.It indicated that the coating has good biocompatibility and bio-mineralization capacity. |
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